Syringe



E. NEIL. SYRINGE.

APPLICATION FILED JUNEY, 1919. 1,343,787. Patented June 15, 1920.

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EWELL NEIL, 0F NASHVILLE, TENNESSEE.

SYRINGE.

Specification of Letters Patent.

Patented June 15, 1920.

Application filed June 7, 1919. Serial No. 302,385.

To all whom it may concern:

Be it known that I, EwnLL NEIL, of Nashville, in the county of Davidson and State of Tennessee, have invented certain new and useful Improvements in Syringes; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

In the medical and dental professions glass syringes are extensively used because they are easily kept clean and in sanitary condition. An objection to this type of syringe is that after it has been filled with injecting fluid and the air expelled move ment of the syringe may result in slight relative displacement of the plunger which Wlll draw air into the syringe. Especially is this true where the needle is pointed upwardly, the Weight of the piston tending to draw it from the barrel and to suck inthe air. Grave consequences may result from injection of an air bubble into the human tissues, and it is the primary object of my invention to provide an improved and simple means for controlling the movement of the piston inthe barrel in all positions of the syringe, such means preventing a movement of the piston save through positive action by the operator. A further object is to provide a positive control which will at all times be in position and which cannot become lost in the sterilization of the parts of the syringe, and a further object is to so locate this piston control as to prevent contact thereof with the hands.

In the accompanying drawing, Figure 1 is a view in side elevation, parts being shown in section. Fig. 2 is a sectional view on line 2-2, Fig. 1.

Referring to the drawings, the barrel formed of glass is shown at 1, the needle at 2, and the piston at 3, the piston having a grip 4 of any preferred form.

The barrel is formed, at that end where the piston is inserted, with a circumferential enlargement 8 which is interiorly recessed or grooved as at 9. The enlargement may be used as a finger hold. Seated within the recess 9 is a split ring 10 preferably of steel, the inner circumference of the ring when seated and in its normal state projecting beyond the longitudinal plane of the inner surface of the barrel, thus lying in the path of the piston when the latter is inserted. In placlng the piston in the barrel the spring 1s expanded and takes a firm grip on the pis ton co-extensive with its circumference. This action causes the ring to be more deeply seated within the recess. Movement of the piston Within the barrel in either direction is readily eifected by positive action, but because of the gripping of the ring the piston cannot move through its own weight and consequently there is no likelihood of air being drawn into the barrel when the needle is pointed upwardly or in any other position of the syringe. It will be seen that after the ring is placed in position in the recess 9 it can only be dislodged by prying and consequently in the washing and sterilization of the syringe there is no chance of the ring being disengaged and lost, and it is also obvious that a syringe constructed after the form described is effectively sterilized with no danger of breaking due to the unequal expansion of the glass and metal parts, the

rlng having a loose but certain connection with the barrel.

I claim as my invention:

1. A syringe including a barrel formed with a circumferential groove in-its inner surface near one end, a'plunger adapted for movement in said barrel adjacent said groove, and a spring loosely fitted in said groove and adapted to grip said plunger to prevent accidental movement of the plunger in the barrel, said groove being of suflicient depth to permit expansion of said spring when the plunger is inserted and said spring being of such diameter as to insure its being retained in said groove when the plunger is withdrawn.

2. A syringe including a' barrel formed with a circumferential recess in its inner surface near one end, a plunger adapted for movement in said barrel adjacent said recess, a split ring seated in said recess, said ring being adapted to be expanded by insertion of the plunger into the barrel and to grip said plunger to prevent accidental movement of the plunger in the barrel.

3. A syringe including a barrel formed with a circumferential enlargement near one end to form a finger-hold, and having a circumferential recess in its inner surface adjacent said enlargement, a plunger adapted for movement in said barrel adjacent said recess, a split ring seated in said recess, said ring being adapted to be expanded by insertion of the plunger into the barrel and to grip said plunger to prevent accidental movement of the plunger in the barrel. 10

In testimony whereof I have signed this specification.

EWELL NEIL. 

